Softeners are small-molecular structures typically applied for the purpose of modifying the texture of the elastomer applied in the chewing gum. A problem when applying softeners to biodegradable polymers is that too extensive use may result in dissolving the polymer before the desired texture is reached.
It is the object of the invention to provide a chewing gum having certain desired texture without dissolving the overall chewing gum structure when adjusting the texture.
It is a further object of the invention to obtain a completely biodegradable chewing gum having a texture comparable to conventional chewing gum.
According to the prior art, a great significance has been made out of glass transition temperature of chewing gum. Especially, when dealing with biodegradable chewing gum.
The glass transition temperature Tg can loosely be defined as the temperature where a polymer undergoes a significant change in properties. The Tg is where a polymer structure turns “rubbery” upon heating and “glassy” upon cooling. Tg is regarded as a so-called second order transition, i.e. a thermal transition that involves a change in heat capacity, but does not have a latent heat.
According to the prior art within the field of chewing gum, e.g. as disclosed in WO 00/19837 and U.S. Pat. No. 5,672,367 great efforts have been made in obtaining a glass transition temperature of the applied chewing gum below about 37° C. In other words, the user of a chewing gum should be able to change the conditions of a chewing gum from below the glass transition temperature to above the glass transition temperature, when the chewing gum in chewed and in fact heated in the mouth.
On the other hand, as it generally applies to chewing gum and e.g. disclosed in U.S. Pat. No. 5,523,098, the glass transition temperature of the chewing gum should not lay significantly below reasonably expected storage temperature, e.g. 10 degrees to 12 degrees C. For this reason a significant effort has been made in order to counteract the expected increase to prevent blocking. Such shipping and storage temperatures are stated to be non-cost-effective. In fact such temperatures may not be possible when shipping in, or to, certain locations. Thus, it is stated in U.S. Pat. No. 5,523,098 that cold flow causes independent gum base pellets or slabs to join or fuse together so that individual slabs or pellets cannot be removed from their container or carton. Pelletized or slab-poured gum base that is stored or shipped at temperatures above its glass transition temperature can deform. Subjected to gravitational forces, these slabs or pellets agglomerate or mass together with other pellets or slabs.
This requirement is reflected in both WO 00/19837 and U.S. Pat. No. 5,672,367 where a biodegradable chewing gum is disclosed comprising one single polymer having a relatively high glass temperature.
However, a drawback of the prior art biodegradable chewing gum is that the biodegradable elastomer polymers by nature perform somewhat different than conventional elastomers. According to the prior art, these deviating properties have dealt with by focussing strictly on keeping the glass transition temperature of the resulting chewing gum below or about 37° C. whereby the desired properties would be obtained.
However, a drawback of the above-described chewing gums is that the final obtainable texture may differ from that of conventional chewing gum.
It is an object of the invention to obtain a biodegradable chewing gum having a texture comparable to conventional chewing gum.
It is an object of the invention to provide both a biodegradable chewing gum that may actually be shipped and distributed under normal or at least substantially conventional chewing gum distribution parameters and on the other hand exhibit an acceptable texture, when applied as a chewing gum.